An Efficient Iterative Approach for Determining the Post-Necking True Stress-Strain Response of Aerospace Metals
To numerically simulate the plastic deformation of aerospace metals during extreme events (e.g., turbine engine blade-out/rotor-burst events and automotive crashworthiness assessment), accurate experimental knowledge of the metal’s hardening behavior at large strains is requisite. Tensile tests on thin (plane stress) specimens are frequently used for this purpose, with the metal’s large-strain plasticity ultimately captured by an equivalent true stress vs. equivalent true plastic strain curve. It is now well known that if axial strain is measured using an extensometer (either physical or virtual), the equivalent true stress-strain curve is valid only up to the onset of diffuse necking, when the strain field heterogeneously localizes in the specimen gage. A number of approaches have been proposed to correct the post-necking strain hardening response. Perhaps the most widely used technique involves inputting a suite of candidate post-necking true stress-strain curves into finite-element software; a tensile test simulation is run for each candidate curve, and the curve that produces the best agreement between simulation and experiment is ultimately adopted. In this talk, a novel variation of this iterative approach is presented that addresses some of its key deficiencies. Notably, we use local/pointwise in-plane Hencky (true) strain data from digital image correlation to generate an upper bound for the iterative simulation process, resulting in an efficient and computationally inexpensive post-necking correction procedure. Our approach is successfully demonstrated using experimental data for both wrought and additively manufactured Ti-6Al-4V titanium alloy.
Robert L. Lowe
Primary Advisor's Department
Mechanical and Aerospace Engineering
Stander Symposium project, School of Engineering
United Nations Sustainable Development Goals
Industry, Innovation, and Infrastructure; Partnerships for the Goals
"An Efficient Iterative Approach for Determining the Post-Necking True Stress-Strain Response of Aerospace Metals" (2020). Stander Symposium Projects. 1854.